My 8th grade science class is building SeaPerch ROVs but they are incredibly positively buoyant with two floats attached to the top side of the PVC frame. I'm looking for ideas of weights to add that will help make these ROVs neutral in the water column. Removing some of the floats is an option but that affects the weight distribution of the ROV causing it to tilt.
Last year we used rocks but they were very difficult to attach to the ROV itself.
Something incremental and water-friendly that we could add about .5-1.5 lbs to one SeaPerch would be ideal.
Thanks for your thoughts!